Our study is centered on the control of transport and accumulation of inorganic phosphate in E.coli via specific membrane transport and via phosphomonoesterase (alkaline phosphatase), polyphosphate kinase and polyphosphatase. Our immediate and specific goals are: a) To analyze the role of the various factors known to be involved in AP synthesis using an in vitro system as an assay. We will purify the products of the positive control gene phoB and of the negative control gene phoR in the hope to obtain a firm confirmation that they control the cell-free synthesis of AP. b) We will study the genetic and physiological role of the transport genes phoS and Phot. In particular we will try to understand the relationship between phoT and phoB genes and the reasons for the selection of phoT-phoB-double mutants in anaerobiosis. We will also analyze the regulation of polyphosphate synthesis as Pi reserve in aerobiosis and in anaerobiosis using various growth conditions.